Sister Full Length Joists Instead of New Beam 1

[SarBear]

Hi everyone, I've got a situation here with a proposed fix that I'm curious if anyone has some input on. I have posted a picture below of the second floor framing plan for a home that is going to be remodeled. The two bubbled walls are to be removed to open up the kitchen. When I was at the home I discovered that the joists over one of the walls break rather than running continuous over the wall (shown below). However, the joists over the beam and the other wall run continuous without breaking. The obvious solution would be to put in a big steel beam that spans across the new open kitchen, but doing so is not feasible on this project.

My question is what if we sister some new, full-length joists to the existing joists instead of putting in a beam? The span from the back of the home to the garage wall is only about 17'-6" which is easily doable for an 11 7/8" joist. I'm not sure why they didn't do that in the first place, but here we are. Has anyone done this before? Any suggestions or concerns?

 

[SarBear]

Thank you all for your responses!

To answer a question that a couple of you have asked about why we don't want to go with a BEAM...The main reason is actually budget. There is another part of the project that I haven't shown because it's not relevant to my question above, but it they are converting the garage that is currently left of the kitchen area into a bathroom, mud room, etc. and then they are adding a third car garage to the left of the current third car garage. They've been talking with the architect and builder for months and came up with this plan based on their budget. The whole remodel revolves around being able to open up this kitchen into a wide open space. So, once they contacted me for the structural engineering I requested the original plans from when they first built the home, which they fortunately had. The old plans didn't show much, but I said we should probably make sure that these interior walls aren't bearing. Lo and behold I discovered that the joists break over that one wall. I told the builder and the owners what's going on and now they are thinking they won't be able to afford the remodel because they hadn't planned on having to do anything structural in this area of the remodel. The builder told them that adding new floor joists would be an additional $2500. I've previously mentioned a couple of the beam ideas (the ones proposed by phamENG above) and the builder has said that he'd be at least $8000 more for the cheapest of those solutions. I won't share my thoughts/opinions on the financial aspect of this situation since they are irrelevant as I'm neither the homeowner nor the builder. Long story short, after proposing some other ideas to the owner and builder I am tasked with finding a solution that involves placing new floor joists over the area.

A couple important things missing from this discussion:

To answer your questions...the wall that we're wanting to bear the new joists on is a wall between the home and a 2-car garage. It is an 8" thick x 9' tall concrete wall with a 24" wide footing...at least that's what the original home plans say. It is currently only bearing some load from the second floor joists, so this added load shouldn't be a problem. Good question about the uplift capacity for the joist hangers to the garage beam. I'll need to go back to the home and see what model those hangers are. The existing floor joists are 11 7/8" TJI/250. Based on some old span charts I could find from Weyerhaeuser it looks like those can span over 19' with a 40 psf live, 20 psf dead, and L/480 deflection.

Sounds like more of you are leaning toward installing LVLs. Fill the web of the existing joists, install a 1.75"x11.875" LVL next to the existing joist and screw through the LVL and joist web, NOT the flange. I would like to do what BAretired suggests and remove the decking and joists and replace everything, but again...$$$.

 

[phamENG]

Interesting. Your drawing makes it look like a 2x4 wall, which is why I was concerned.

For what it's worth, I'm only thinking LVL due to imagined constraints on installation. If you have to make funky end cuts to get it in place, a TJI/I-joist isn't going to work. I have no issues with using a new, full length joist and filling the gap and screwing through the web if it'll fit intact. All it's doing is keeping the old floor just from falling off at that point. But I would suggest you go through and glue and re-fasten the subfloor above to the new joists if that's possible. At least have them glue them to the underside of the floor sheathing (and then make your nailing to the existing joists transfer any loads that may be need to be transferred from the diaphragm, etc.

 

[SarBear]

Ah sorry, it IS a 2X4 framed wall that sits on top of the 8"x9' concrete foundation wall.

The more I think about this the more I'm thinking that the only way to get a new joist or LVL in would be to cut through the rim at the back of the home and then thread through all the way to the garage wall. That existing bearing wall can't be removed until the new joists are in, and I can't think of any shoring that could be done which would allow a new joist to be installed from the inside of the home. Maybe they shore all of the existing joists except for one at a time, thus providing a little "window" to slide a joist up in there (shown below).

 

[XR250]

That existing bearing wall can't be removed until the new joists are in, and I can't think of any shoring that could be done which would allow a new joist to be installed from the inside of the home. Maybe they shore all of the existing joists except for one at a time, thus providing a little "window" to slide a joist up in there (shown below).

They will figure it out.

 

[phamENG]

Don't try to game out the sequence - that's the contractor's job. Make sure there is a workable sequence, for sure, but let them handle the means and methods of construction. Your insurance broker will thank you...

 

[dhengr]

SarBear:
And, while the budget won’t allow for proper structuring of this screwed up mess, and they didn’t bother thinking about structure until the last minute, don’t forget the 2000lb. marble topped island they are wanting to put in the middle of the kitch. span, with its many chain sawed mech. penetrations through the TJI’s. When we (SE’s) are almost always the last one’s invited to the party, the budget is always more than spent on plumbing, mech. and electrical fixtures and counter tops before anyone asks, ‘ given what we are starting out with, do you still want it to stand up to the rigors of usage, over time?’

 

[80PercentTruth]

Nice solution. I would have installed a flush LVL beam within the floor cavity with end joist hangers given the ease of construction, but there is nothing wrong with this approach. Amazing you were able to find drawings of the existing home...I see too many walls opened up with beams/posts without checking the foundation that is there...you can't put a concentrated post load on a 4" slab. Install a proper footing or spread the load sufficiently.

"Engineers only know about 80% of the truth, the next 10% is very difficult to achieve, and the last 10% impossible. If we are bound to be wrong, we may as well be wrong simply and conservatively."